The present invention relates in general to heat exchangers and more specifically to a high fin density coil design utilizing precoated fin stock.
The use of fins attached to fluid containing tubes to dissipate heat from a contained liquid is well known. Generally, a series of tubes carry heated liquid and form a cooling system. The tubes have metal fins attached thereto which form heat dissipating means. The fins are typically made of aluminum or copper.
The fins may be elongated, thin strips of aluminum with the width and length of the fins depending upon the number, diameter and configuration of the tubes. Generally, the fins may be held in place by a force fit over the tubes or may be adhered to the tubes by solder.
In order to provide an aesthetically pleasing look, it has been found advantageous to provide a coating on surface of the fins. It has been observed that system performance problems occur due to the thermal resistance typically found on high fin density coil designs when conventional (full coat) precoated fin stock is used for coil construction. These problems are particularly prevalent when a coated fin stock is utilized on a high fin density,  greater than 17 FPI (fins per linear inch), and even more so when  greater than 20 FPI, in coil designs applicable to residential outdoor products.
It should be noted that low fin density coils (10-15 FPI) don""t have as much or a significant amount of thermal resistance due to a coating on the fin stock. It is more important to deal with this problem for high fin density coils.
A problem associated with a uniform coating pattern is such that the pattern near the outer edges of the fin stock, because of the drawing operation within the fin die, results in coating material being forced within the collars and also produces fins having a bare fin edge that will have to be scrapped.
It is therefore an object of the present invention to overcome the problems of the prior art described above.
It is another object of the present invention to utilize a patterned fin stock which eliminates significant thermal resistance typically present in conventional precoated fin stock used on high fin density heat exchangers.
It is yet another object of the present invention to effectively use a patterned fin stock on high fin density coil designs.
It is a further object of the present invention is to provide a staggered coating pattern to compensate for the drawing operation in forming the fin collars and assure accurate positioning of the coating pattern at the outer edges of the fin stock.
The primary object of the present invention to provide a method of designing a patterned fin stock which eliminates or minimizes coating material from within the collars to insure efficient coil performance across a range of fin densities.
The present invention relates to the use of striped fins on high fin density heat exchangers. High fin density applications have reduced contact between the collars on fins and tubing because of the shortened collar length of the individual fins. Therefore it is important to eliminate precoating from the collars more so than on low fin density applications. In order to overcome the problem of the coating material being drawn into the inside of the fin collar and adversely effecting coil performance, it was determined that the conventional uniform spacing of the fin stripes had to be changed. It was discovered that if the stripe pattern near the edges of the fin stock was spaced further or staggered from the center of the sheet that this effectively compensated for the drawing operation with the fin die.
This concept minimizes the chance of drawing the painted (coated) portion within the collars of the outer row of the fin die, and also avoids the potential of having a bare or uncoated fin edge on the fabricated plate fins from the patterned fin stock. A bare fin edge would present an inconsistent appearance and would have to be scrapped.